Solidoodle 4 print issue solved (Page 1 of 2)

Thanks for the info I too have been struggling with the circles not being circles. found the left carriage cracked  and glued it. found the the left panel hitting the y cartridge assembly the end of a shaft rubbing . corrected these problems and the circles are worse not better. . nine has no extra support block. the frame is flimsy at best . I am tempted to start from scratch and use the sd4 as a 3d drawing to work off of. And build one right.
I started making aluminum carriage brackets.
tin

It's very nice of you to share your findings.
But unfortunately I don't think you've figured out completely what the actual  issue is.
You're right that the extra support bearing (bushings) they added causes binding, but not because it is not positioned correctly or the rod is bent.

I've posted about the issue in another thread.
http://www.soliforum.com/topic/8199/odd … s/page/19/

My SD4 doesn't have a bent rod and I've tried printing both with the support bearing block on and without it. It's true that the support bearing causes more binding. But it's not true that removing this upgrade in SD4 and making it like it was in SD3 solves the issue.
Here's the problem:

Solidoodle uses bushings instead of (ball) bearings. Bushings might be cheaper but they cause a lot more friction than bearings.
Check this video: https://www.youtube.com/watch?v=50rUzUHek8E

So when Solidoodle added the pillow block (support bushing), the point was to prevent the rod from bending from the y motor belt pulling it down, but it also introduces the worse side effect of getting binding because there is now a bushing right next to the bending part which adds a lot of friction and the motor can't handle it. Solution is loosening the belt, but that introduces backlash because the belts aren't tight enough.

I posted how I switched to ball bearings here: http://www.soliforum.com/post/74861/#p74861

Now I can tighten the belts as much as I want without getting binding, which was not the case with the stock bushings even with the support bushing piece taken off.

(The carriage also uses bushings in instead of bearings, jagowilson's (lawsy's) mod might give the same results by reducing the friction there instead. http://www.soliforum.com/post/72175/#p72175 )

But I haven't gotten rid of backlash. It's much better now, but it's still there.

before

after

So yeah, I don't know how to fix the issue completely. Just letting you know getting a good Y shaft and taking out the support bushing ("pillow block") won't solve your backlash issue.
And that I can tighten the belt as much as I want without binding and the backlash is still there.

And I'll need to get a SD3 and check it out to make sure SD3 doesn't have this problem. I've seen some which print just fine and some which have the same backlash issue. Might be caused by switching to low quality rod, bushing or belt by the company at some point. That, or most of us being terrible at adjusting the Y motor belt tension (unlikely, I think).

You should be able to post images uploaded to a site from imgur.com. I have seen some users with only 2 posts share pics.

Another member here, Claghorn, designed a pillow bearing block which allows alignment to be adjusted:

http://home.comcast.net/~tomhorsley/har … aring.html

So what did you change for that print?
Hard to tell how perfect the circles afre from the slight photo angle and missing final small circle (unless you used a different STL)
But doesn't look as bad as stock for sure.

here's mine

This one's new to me.
So your belts are on the bearings?

Uh, cool.
What did you do though?

The poor circles were a result of belt lash. The belt lash is caused by reversing the load on the belts. I created a tensioning device that loads the belts in one direction. I made it work with a makeshift setup, but I'm going to make a proper fix when I get back next week.

With the tensioner, you don't need super tight belts anymore, so the bearing mod isn't necessary.

My tensioner is very different from that design. It doesn't tighten the belt.  It eliminates the lash by eliminating load reversing on the belt. I'll post pics when I set it up next week.

Actually a direct drive on Y drive (6mm rear rod) is a best way to reduce
Backlash on Y belt, but if we keep stock y drive, your mod seems
working well, so please post the pictures to show all changes you did.

I'm still tweaking it and making some parts. Just got back from a trip, but I should have time this weekend to get it running properly. I plan on converting to direct drive, probably next month. I'd still like to get this thing running properly so that I can make parts for my conversion. I also plan on upgrading to a 8 mm shaft for the y-drive, with ball bearings at each end. I'm also upgrading the belts and pulleys to gt2 for the y and x axis. I'm planning a new carriage design using linear bearings as well. I'm using this for prototyping several inventions I have in the works, so I need some pretty accurate precision. If my mods don't work out, I'll build a new printer.

I think I've got everything figured out now. Just need to print a couple parts and put it together.